(1) Field of the Invention
The invention is related to a bracket for connecting a traverse of a landing gear to a cabin of a helicopter with the features. The invention is further related to the application of an inventive attachment with said brackets for connecting a traverse of a landing gear to a cabin of a helicopter.
(2) Description of Related Art
Vibrations or resonance modes are produced, when a helicopter (HC) lands for example on the front part of its landing gear (LG), e.g. when landing on a slope. Those resonance frequencies and resonance modes can cause the HC to become inoperable due to ground resonance. A landing gear assembly comprises typically a pair of cross tubes or traverses and a pair of struts connected at the outboard ends of said cross tubes or traverses.
The document U.S. Pat. No. 4,270,711 A discloses a helicopter landing gear assembly with a pair of cross tubes having a pair of struts connected at the outboard ends thereof. A first of the cross tubes is connected to the helicopter fuselage at a pair of laterally spaced points. The second of the cross tubes is joined by a pivot connection to a structural bridge positioned above the second cross tube. The structural bridge is connected at its outer ends to the fuselage main beams. The structural bridge connected to the second cross tube permits the helicopter fuselage to pivot about a fore-aft axis thereof to lower the natural roll frequency of the helicopter airframe and therefore increase the margin of stability to prevent ground resonance.
The document U.S. Pat. No. 6,244,538 B1 discloses a skid landing gear for a helicopter, in which the directional stiffnesses of the cross members of the skid landing gear have been de-coupled from one another, such that optimization of the longitudinal stiffness of the cross members may be performed independently of the optimization of the vertical stiffness and fatigue life of the cross members. In order to de-couple the stiffnesses in the skid type landing gear, two approaches are employed. In the first approach, the skid landing gear has non-symmetric-section cross members and/or distribution of different materials within the cross-section for de-coupling the vertical stiffness of the cross members from the longitudinal stiffness, such that placement of the ground resonance frequency may be optimized, while retaining the vertical stiffness properties essential for optimizing vertical energy attenuation and fatigue life. In the second approach, mounting devices are employed that provide compliance in selected directions, thereby de-coupling the directional stiffnesses.
Said helicopters known from the state of the art require specific adaption of the landing gears and/or cabins for the prevention of ground resonance.